Intermediate power down mode for a rotatable media data storage device

ABSTRACT

The power consumed by a data storage device having at least one disk connected with a spindle can be reduced by reducing the rotation rate of the spindle to a rotation rate greater than zero. In one method in accordance with the present invention, wherein a head is in communication with each disk, the spindle can be rotated at a first rotation rate. The head can be parked and the rotation of the spindle can then be reduced to a rotation rate greater than zero. By reducing the rotation rate of the spindle, the power consumed by the spindle can be reduced by approximately the ratio of spin speeds to the exponential power of 1.5. This description is not intended to be a complete description of, or limit the scope of, the invention. Other features, aspects, and objects of the invention can be obtained from a review of the specification, the figures, and the claims.

PRIORITY CLAIM

[0001] This application claims priority to the following U.S.Provisional Patent Application:

[0002] U.S. Provisional Patent Application No. 60/436,946, entitled“Intermediate Power Down Mode for a Rotatable Media Data StorageDevice,” Attorney Docket No. PANA-01062US0, filed Dec. 30, 2002.

FIELD OF THE INVENTION

[0003] The present invention relates generally to rotatable media datastorage devices, as for example magnetic or optical hard disk drivetechnology, and power consumption of rotatable media data storagedevices.

BACKGROUND OF THE INVENTION

[0004] Over the past few years, notebook computers have becomeprogressively thinner and lighter, and battery technology has improvedsignificantly; but, though both thinner and lighter, notebook computershave incorporated ever-more powerful CPU's, larger and higher resolutionscreens, more memory and higher capacity hard disk drives. Feature-richmodels include a number of peripherals such as high-speed CD-ROM drives,DVD drives, fax/modem capability, and a multitude of different plug-inPC cards. Each of these features and improvements creates demand forpower from system batteries. Many portable electronics, such as MP3players and personal digital assistants, now use rotatable data storagedevices as well, and by their nature and size place great demands forpower on batteries.

[0005] Many manufacturers of rotatable data storage devices reducedemand on batteries by employing power savings schemes; for example,many manufacturers ramp down and stop a rotating storage medium after aperiod of inactivity. This scheme comes at a cost to performance—themedium must be spun up from standstill before information can beaccessed from the medium.

BRIEF DESCRIPTION OF THE FIGURES

[0006] Further details of embodiments of the present invention areexplained with the help of the attached drawings in which:

[0007]FIG. 1A is a partial perspective view of an arrangement utilizinga method in accordance with one embodiment of the present invention.

[0008]FIG. 1B is a close-up view of a head suspension assembly used inan arrangement as shown in FIG. 1A showing head, slider and suspension.

[0009]FIG. 1C is an illustration of the rotary motion of the headsuspension assembly of FIG. 1B across the surface of a disk.

[0010]FIG. 2 is a graph showing the power consumed in the differentmodes of a typical power management scheme by an arrangement such asshown in FIG. 1A.

[0011]FIG. 3 is a graph roughly showing the relationship between powerconsumed by a spindle and the spin speed of the spindle in anarrangement such as shown in FIG. 1A.

DETAILED DESCRIPTION

[0012] FIGS. 1A-C illustrate one embodiment of an arrangement 100contained within a hard disk drive for utilizing a method in accordancewith the present invention. FIG. 1A is a partial perspective view of thearrangement 100 that comprises three disks 120 attached to the hub of aspindle 110. The disks 120 can be made of a light aluminum alloy,ceramic/glass or other suitable substrate, and coated on one or bothsides with a magnetizable material. The magnetic layers have tinydomains of magnetization for storing data transferred through heads. Theinvention described herein is equally applicable to technologies usingother mediums, as for example, optical mediums. Further, the inventiondescribed herein is equally applicable to devices having any number ofdisks attached to the hub of the spindle motor. Most hard disk driveshave at least two disks. The disks 120 are connected with the rotatingspindle 110 (for example by clamping), spaced apart to allow heads 146(shown in FIG. 1B) to access the surfaces of each disk, and rotated inunison at a constant set rate ranging from 3,600 to 15,000 RPM, withspeeds of 4,200 and 5,400 RPM being common for hard disk drives designedfor mobile environments, such as laptops.

[0013] An actuator assembly 130 (shown partially in FIGS. 1A-C) sweepsan arc, as shown in FIG. 1C, between the inner diameter of the disks 124a and the outer diameter of the disks 124 b, that combined with therotation of the disks 120 allows ahead 146 to access approximately anentire surface of a disk 120. The heads 146 read and/or write data tothe disks 120. A head 146 can be said to be in communication with a disk120 when reading or writing to the disk 120. Each side of each disk 120can have an associated head 146, and the heads 146 are collectivelycoupled to the actuator assembly 130 such that the heads 146 pivot inunison. When not in use, the heads 146 can rest on the stationary disks120 (typically on an inner portion of the disks that does not containdata) or on a ramp 150 positioned either adjacent to the disks 120 orjust over the surfaces of the disks.

[0014]FIG. 1B details an example of a subassembly commonly referred toas ahead suspension assembly (HSA) 140, comprising the head 146 attachedto a slider 144, which is further attached to a flexible suspensionmember (a suspension) 142. The spinning of the disk 120 creates airpressure beneath the slider 144 that lifts the slider 144 andconsequently the head 146 off of the surface of the disk 120, creating amicro-gap of typically less than one micro-inch between the disk 120 andthe head 146 in one embodiment. The suspension 142 is bent or shaped toact as a spring such that a load force is applied to the surface of thedisk. The “air bearing” created by the spinning of the disk 120 resiststhe spring force applied by the suspension 142, and the opposition ofthe spring force and the air bearing to one another allows the head 146to trace the surface contour of the rotating disk surface, which islikely to have minute warpage, without “crashing” against the disksurface. When ahead “crashes” the head collides with a surface such thatthe head is damaged.

[0015] Many hard disk drives designed for mobile environments supportpower management. Such a hard disk drive may have different operating“modes”, including reduced power modes in which hard disk driveperformance is reduced, thereby improving battery lifetime.

[0016]FIG. 2 charts the power consumption of a hard disk drive employinga power savings scheme. A typical power savings scheme operates the harddisk drive in four different modes: an active mode (T<0 sec., where T isthe inactive time interval)), an idle mode (0<T<10 sec.), a standby mode(10 sec.<T<300 sec.), and a sleep mode (initiated by the user). Itshould be noted that the inactive time intervals for each mode can varysubstantially between hard disk drives and between generations of harddisk drives. In active mode, the hard disk drive seeks, reads andwrites, generally consuming between 2-2.5 Watts. The hard disk drivewill remain in active mode typically up to five to ten seconds followingthe completion of a command before entering into idle mode. In idlemode, specific electronics are turned off to reduce power consumptionwhile still providing a relatively quick recovery. Power savings schemesvary in their methods for reducing power to the actuator 130. In onepower savings scheme either the heads 146 are moved to a parkingposition over the disk surface and the servo tracking function is turnedoff or operated at a reduced level of control, or the hard disk drivemay servo every fourth servo sample thereby reducing the powerdissipated by actively reading. The disks 120 continue spinning at theactive mode speed and the interface electronics remain ready to acceptcommands. Power consumption can be reduced to less than 1 Watt in idlemode, but the hard disk drive can take anywhere from about 20 to 100milliseconds to return to active mode.

[0017] After the hard disk drive has been inactive for a predefinedperiod of time, usually at the user's discretion but typically fiveminutes, the hard disk drive will enter standby mode. In standby mode,the heads 146 are moved to a parking position on a ramp 150 adjacent toor just over the disks 120, the spindle 110 and the disks 120 arestopped and most of the electronics are powered off. Power consumptionis reduced to less than 0.5 Watts, but recovery time (the time requiredto return to active mode once a command is received) jumps to anywherefrom approximately one second to as many as thirty seconds.

[0018] Sleep mode is entered by a specific command, and is used for longperiods of inactivity. All electronics are powered off except thoseneeded to return to active mode. Power consumption is reduced to about0.1 Watts, but recovery time is longer than for standby mode.

[0019] Hard disk drives can have more or fewer modes than thosedescribed above, with each mode comprising different combinations ofpower saving measures. The example described above is one power savingsscheme. Manufacturers may select a power savings scheme by balancing theneed for performance against the need mobility, for example.

[0020] In one embodiment a method in accordance with the presentinvention includes an intermediate power down mode activated after aperiod in idle mode, with the period being predefined or set as desired,for example by the user. In intermediate power down mode, the heads 146are unloaded from the disk 120 and parked on a ramp 150. In otherembodiments, the heads 146 may be parked on the disks 120. The power tothe spindle 110 is then reduced, thereby reducing the rotation of thespindle 110 and the disks 120. In one embodiment, an intermediate modespin speed of the spindle 110 is an optimal speed such that the spindle110 can be brought back up to active mode spin speed in approximatelythe same amount of time it takes for the heads 146 to load from the ramp150 to the disks 120. In active mode, the power consumed by the rotationof the spindle can be roughly fifty percent of the overall powerconsumed by the hard disk drive, and as much as eighty percent of theoverall power consumed by the hard disk drive with the heads 146 parkedand the actuator 130 turned off; therefore, a significant savings inoverall hard disk drive power consumption is observed by reducing thepower consumption of the spindle 110.

[0021]FIG. 3 graphically represents a rough approximation of therelationship between power consumption by the spindle 110 and spindlespeed in accordance with one embodiment. Power consumption by thespindle 110 increases by approximately the ratio of spindle speeds tothe exponential power of 1.5. For example, a hard disk drive spindle 110operating at 5400 RPM in active mode consumes approximately forty-fivepercent less power rotating at 3600 RPM in intermediate mode.

[0022] In alternative embodiments, it maybe desired that the spindlespeed is further reduced. For example, it may be desired that sometrade-off in performance be made for additional power savings. Byfurther reducing spindle speed a lag time is introduced. The heads 146should not be loaded onto the disk 120 while the spindle 110 is at avery low speed. A threshold spindle speed must be reached to maintainthe air bearing between the slider and the disk, and avoid crashing theheads 146. Once this threshold spindle speed, or ramp load speed, isreached the heads 146 maybe loaded onto the disks 120, but must delayexecuting a command until the spindle 110 reaches active mode spindlespeed. The intermediate power down mode still achieves significantbenefits in performance over standby mode by eliminating start-uptransients that result when ramping from standstill.

[0023] In still other embodiments, it may be desired that the spindlespeed be reduced to a speed greater than the optimal speed. It maybedesired that a benefit is gained from reduced power consumption whileensuring that the hard disk drive responds to commands as quickly aspossible.

[0024] In some embodiments, the heads 146 remain on the disk surfacerather than parked on the ramp 150. The rotation of the spindle 110 andby extension the disks 120 can be slowed to a speed that will allow alag time between receiving a command and executing a command, duringwhich time the spindle 110 ramps up to active mode speed, providing whatmaybe an acceptable trade-off between performance and power savings. Thedisks must be maintained at or above the threshold spindle speed toavoid crashing the heads.

[0025] It is noted that the embodiments including arm-loading ramps donot suffer any time delay due to a disk spinning in a slower orintermediate power-down mode, as the disk spin-up time is generallysimilar to the time required for loading the arm onto the disk from theramp.

[0026] The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many modifications andvariations will be apparent to one of ordinary skill in the relevantarts. The embodiments were chosen and described in order to best explainthe principles of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications that are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the claims and their equivalence.

1. A method to reduce the power consumed by a data storage deviceincluding a disk and an actuator having a head positioned over the disk,comprising: rotating the disk at a first rotation rate; and reducing therotation of the disk to a second rotation rate greater than zero.
 2. Themethod of claim 1 wherein the first rotation rate is 5400 RPM.
 3. Themethod of claim 2 wherein the second rotation rate is 3600 RPM.
 4. Themethod of claim 1 wherein the first rotation rate is one of 4200 RPM,7200 RPM, 10000 RPM, and 15000 RPM.
 5. The method of claim 1, whereinthe second rotation rate is the minimum rotation rate at which the diskcan rotate such that an air bearing between the head and the disk ismaintained.
 6. The method of claim 1, wherein the method includes thestep of positioning a flexible member connected with the head on a rampprior to reducing the rotation of the disk to a second rotation rategreater than zero.
 7. The method of claim 1, wherein the method includesthe step of positioning a flexible member connected with the head on aramp while reducing the rotation of the disk to a second rotation rategreater than zero.
 8. The method of claim 6, wherein the second rotationrate is the minimum rotation rate at which the disk can rotate so thatthe rotation of the disk can be increased to the first rotation rate inapproximately the time required for the flexible member to be positionedover the disk.
 9. A data storage device adapted to perform the method ofclaim
 1. 10. A method to reduce the power consumed by a data storagedevice comprising the steps of: providing one of a hard disk drivehaving at least one disk, an optical drive having at least one disk, anda magneto-optical drive having at least one disk, wherein the at leastone disk is rotating at a first rotation rate, and an actuator assemblyhaving at least one head, wherein the at least one head is incommunication with the at least one disk; removing the at least one headfrom communication with the at least one disk; and reducing the rotationof the at least one disk to a second rotation rate greater than zero.11. The method of claim 10, wherein the second rotation rate is theminimum rotation rate at which the at least one disk can rotate so thatthe rotation of the at least one disk can be increased to the firstrotation rate in approximately the time required for the at least onehead to reestablish communication with the at least one disk.
 12. Amethod to reduce the power consumed by a data retrieval devicecomprising the steps of: providing a data retrieval device having atleast one disk, wherein the at least one disk is rotating at a firstrotation rate, an actuator assembly having a laser, wherein the laser isin communication with the at least one disk, and a servo system;removing the laser from communication with the at least one disk; andreducing the rotation of the at least one disk to a second rotation rategreater than zero.
 13. A method to reduce the power consumed by a datastorage device comprising the steps of: providing a data storage devicehaving at least one disk, wherein the at least one disk is rotating at afirst rotation rate, an actuator assembly having at least one head, anda servo system; receiving a signal to reduce the rotation rate of the atleast one disk; reducing the rotation of the at least one disk to asecond rotation rate greater than zero; receiving a signal to perform anoperation; and increasing the rotation of the at least one disk to thefirst rotation rate.
 14. The method of claim 13, wherein the secondrotation rate is the minimum rotation rate at which the disk can rotatesuch that an air bearing between the head and the disk can bemaintained.
 15. The method of claim 13, wherein the method includes thestep of positioning a flexible member connected with the head on a rampprior to reducing the rotation of the disk to a second rotation rategreater than zero.
 16. The method of claim 15, wherein the secondrotation rate is the minimum rotation rate at which the disk can rotateso that the rotation of the disk can be increased to the first rotationrate in approximately the time required for the flexible member to bepositioned over the disk.
 17. A method to reduce the power consumed by adata storage device comprising the steps of: providing a data storagedevice having at least one disk, wherein the at least one disk isrotating at a first rotation rate, an actuator assembly having at leastone head, wherein the at least one head is in communication with the atleast one disk, and a servo system; receiving a signal to reduce therotation rate of the at least one disk; removing the at least one headfrom communication with the at least one disk; reducing the rotation ofthe at least one disk to a second rotation rate greater than zero;receiving a signal to perform an operation; increasing the rotation ofthe at least one disk to the first rotation rate; and placing the atleast one head in communication with the at least one disk.
 18. Themethod of claim 17, wherein the steps of increasing the rotation of theat least one disk to the first rotation rate and placing the at leastone head in communication with the at least one disk are performedsimultaneously.
 19. The method of claim 18 wherein the second rotationrate is the minimum rotation rate at which the at least one disk canrotate so that increasing the rotation of the at least one disk to thefirst rotation rate is approximately the time required for placing theat least one head in communication with the at least one disk.
 20. Themethod of claim 17, wherein the step of removing the at least one headfrom communication with the at least one disk further includespositioning the actuator assembly onto a ramp such that the at least onehead is adjacent to the at least one disk.
 21. The method of claim 17,wherein the step of removing the at least one head from communicationwith the at least one disk further includes positioning the actuatorassembly such that the at least one head is over an outer portion of theat least one disk.
 22. The method of claim 17, wherein the firstrotation rate is 5400 RPM.
 23. The method of claim 22, wherein thesecond rotation rate is 3600 RPM.
 24. A method to reduce the powerconsumed by a data storage device comprising the steps of: providing adata storage device having at least one disk and an actuator assembly incommunication with the at least one disk, wherein the at least one diskis rotating at a first rotation rate; and reducing the rotation of theat least one disk to a second rotation rate greater than zero.
 25. Amethod to reduce the power consumed by a data storage device comprisingthe steps of: providing a data storage device having at least one disk,wherein the at least one disk is rotating at a first rotation rate, anactuator assembly having at least one head, wherein the at least onehead is in communication with the at least one disk, and a servo system;receiving a signal to reduce the rotation rate of the at least one disk;reducing the rotation of the at least one disk to a second rotation rategreater than zero; receiving a signal to perform an operation;increasing the rotation of the at least one disk to the first rotationrate.
 26. The method of claim 25 wherein the second rotation rate is theminimum rotation rate at which the at least one disk can rotate so thatincreasing the rotation of the at least one disk to the first rotationrate is approximately the time required for placing the at least onehead in communication with the at least one disk.
 27. A system forstoring and retrieving information, comprising: at least one disk; aspindle connected with the at least one disk such that the at least onedisk rotates at a first rotation speed; a head adapted to be incommunication with the at least one disk; and an actuator assemblyadapted to position the head over the at least one disk; wherein after atime has elapsed following receipt and execution of a first command, therotation of the at least one disk is reduced to a second rotation speedgreater than zero.
 28. The system of claim 27, wherein the rotation ofthe at least one disk is increased from the second rotation speed to thefirst rotation speed after a second command is received.
 29. The systemof claim 28, wherein the at least one head is removed to a ramp prior toreducing the rotation of the at least one disk to the second rotationspeed.
 30. The method of claim 29 wherein the second rotation rate isthe minimum rotation rate at which the at least one disk can rotate sothat increasing the rotation of the at least one disk to the firstrotation rate is approximately the time required for placing the atleast one head in communication with the at least one disk.
 31. A methodof manufacturing a data storage device with improved power managementcapability, comprising: providing means for rotating an at least onedisk at a first rotation rate, the at least one disk having an actuatorarm in close proximity to a first surface of the disk; providing meansfor removing the actuator arm from close proximity to the first surfaceof the disk; and providing means for reducing the rotation of the atleast one disk to a second rotation rate greater than zero.
 32. A systemfor storing and retrieving information, comprising: a rotatable meansfor storing data; a means for rotating said rotatable means at a firstrotation speed; and a means for reading and writing data to therotatable means; wherein after a time has elapsed following receipt andexecution of a first command, the rotation of the rotatable means isreduced to a second rotation speed greater than zero.
 33. The system ofclaim 28, wherein the rotatable means is a disk having at least onemagnetic layer.
 34. The system of claim 32, wherein the means forrotating said rotatable means is a spindle.
 35. The system of claim 32,wherein the means for reading and writing data to the rotatable means isan actuator assembly having a head.
 36. A processor having instructionsfor: rotating an at least one disk at a first rotation rate, the atleast one disk having an actuator arm in close proximity to a firstsurface of the disk; removing the actuator arm from close proximity tothe first surface of the disk; and reducing the rotation of the at leastone disk to a second rotation rate greater than zero.
 37. A method toreduce the power consumed by a data storage device including a disk andan actuator having a head positioned either over the disk or in anoff-disk position, comprising: rotating the disk at a first rotationrate; and reducing the rotation of the disk to a second rotation rategreater than zero.